1. Field of the Invention
The present invention relates to a gas cooking apparatus with a glass/glass-ceramic plate providing a cooking surface which has at least one cooking area, with a gas burner whose burner ring is supplied a mixture of gas and primary air to form an open flame and which is associated with an opening in the glass/glass-ceramic plate and with a cooking vessel support arranged over the gas burner.
The present invention also relates to a cooking vessel support for this type of cooking apparatus.
2. Prior Art
A gas cooking apparatus with a glass-ceramic plate providing a cooking surface and cooking area, which is heated electrically, has been marketed commercially for more than two decades. These glass-ceramic cooking units are valued because of their pleasing appearance, the flat work surface and the ease with which they are cleaned. Because of these definite, highly esteemed advantages which are associated with glass-ceramic material as a cooking surface material, for a few years now attempts have been made to use this material in gas cooking apparatus or in cooking units with electrically heated cooking zones combined with gas burners, the so-called mixed or duo-units.
Two types of gas cooking apparatus have been built with this type of cooking surface. In one type a radiant gas burner is provided which is arranged under a cooking area on a closed glass-ceramic plate. In this type of gas burner the gas is burned on the surface of a burner plate made from porous and/or perforated ceramic material or from a fleece, fiber mat or web of ceramic or metal fibers. The radiant heat produced thereby is the essential component of the heat supplied to the heating area or zone. This kind of cooking apparatus unit is for example disclosed in German Patent Document DE 43 26 945 C2.
In the second type conventional atmospheric gas burners, i.e. those with an open flame, arising from holes provided in the largely sealed glass-ceramic plate, are used. The respective cooking vessel is placed on the so-called cooking container support, which is placed on the glass-ceramic plate. Moreover the so-called hybrid burner is known, in which a portion of the energy is also transmitted to the vessel by radiation besides the energy transfer by convection that occurs with an open flame.
The present invention is based on a gas cooking apparatus with gas burner having an open flame, for example as disclosed in the German Patent Documents DE 195 05 469 C1, DE 41 33 409 A1 or DE 44 42 572.
In cooking apparatus of the above-described type the respective cooking vessels typically are supported at the height of the cooking container or vessel support at a higher level than that of the conventional cooking surface that is provided by the glass/glass-ceramic plate. This has been found to be very troublesome especially in the above-mentioned duo-apparatus with electro-cooking areas and gas burner areas. The stability of the cooking vessels is seen to be a problem because of the large height differences between the gas burner areas and the electro-burner areas.
Combustion engineering considerations place a limit on efforts to keep the cooking vessel support as small as possible in the known embodiment of the gas burner positions.
A portion of the required combustion air is supplied as primary air with the gas stream at the known gas burner positions with gas burners having open flames. In the above-cited 195 05 469 C1 the primary air is supplied at the side of the glass-ceramic plate through suitable air entrance openings from outside into the space under the glass-ceramic plate. In the above-cited DE 44 42 572 C1 the supply of primary air occurs from outside under the glass-ceramic plate through aeration slots in the bushing ring, with which the opening in the glass-ceramic plate for the gas burner is enclosed. In both cases the supplied primary air from the outside is mixed with the gas fed to the burner by means of known devices. The remaining combustion air is guided to the flame as secondary air from above, i.e. above the glass-ceramic plate into the space between the vessel bottoms, flowing in from outside. Also the burned exhaust gas must be fed into the same space. For this reason minimization of the spacing between the glass-ceramic cooking surface and the bottom sides of the cooking vessels and thus the vessel support height is required in order to provide clean combustion and an efficient energy transfer.
When the bottom side of the cooking vessel is too close to the flame of the atmospheric burner, the exhaust gas quality is clearly poorer and the flames wander to the exterior in order to obtain secondary air required for combustion, whereby the energy transfer would be dramatically poorer, and, on account of unburned gas ingredients, the flames could flash back in a detonation or with a puff on removal of the cooking vessel from the cooking apparatus. Furthermore there is a danger that the flames come up to the vessel.
The currently known atmospheric burner thus requires a vessel support height of from 30 to 60 mm because of this reason. As a result there is a cooking vessel instability risk due to this height difference between the two different cooking planes (gas cooking plane and electro-cooking plate) or between the gas cooking plane and the height of the working plate and the ergonomics is not optimum.
It is an object of the present invention to clearly reduce the vessel support height required because of combustion engineering considerations while retaining the conventional exhaust gas quality and the efficiency of the gas burner, to clearly reduce the risk of cooking vessel instabilities due to the different heights of different areas and to improve the ergonomics of the cooking apparatus.
According to the invention the cooking apparatus of the above-described kind includes means for supplying substantially all of the primary and secondary air for combustion from the chamber or space under the glass/glass-ceramic plate to the open flame or flame region of the gas burner.
Because of the features according to the invention conventional vessel support height in the current atmospheric burner can be reduced in a surprising manner. In the case of the invention the secondary air is not guided from the outside to the flame from the upper side of the cooking surface, but instead from a level under the bottom side of the cooking surface of the cooking apparatus, i.e. from the cooking apparatus interior. Because of this very simple, but completely effective measure the spacing of the cooking surface to the vessel bottom can be reduced to the extent that only the still cleanly burned exhaust gas, which flows directly to the bottom of the cooking vessel must be exhausted and simultaneously a secondary air supply need not be secured from the outside. This simple feature has the surprising consequence that a definite reduction of the vessel support height to a height not greater than 25 mm results for the known atmospheric gas burner. In the current atmospheric gas burner which requires a vessel support height of 30 mm in the currently known structure in order to guarantee optimum combustion and sufficient energy transfer, a reduction of the vessel support height of only 5 mm causes about a 10-fold increase in the CO exhaust gas content. When a secondary air supply according to the invention is guaranteed from the cooking apparatus interior, the CO exhaust gas content remains substantially unchanged.
In conventional structures the reduction of the container or vessel support height had a negative effect, namely the flames are lowered and wander to the outside because of an insufficient air supply in addition to the negative effect already mentioned above. Because of that energy transfer is understandably considerably reduced. Also this effect is avoided by secondary air supply from the cooking apparatus interior through the opening in the glass-ceramic plate directly to the flame region of the gas burner. Based on this simple feature and the resulting positive effect an entirely new structural unit may be designed for gas and duo-units. A desire for increased stability for the vessels placed on the cooking apparatus and improved ergonomics can thus be fulfilled.
The clearly reduced vessel support height also exerts a decisive positive influence on the esthetics of the cooking apparatus.
In an especially preferred embodiment a blower is arranged in the chamber or space under the glass/glass-ceramic plate to assist in supplying secondary air.
In principle the structure can be designed so that the burner ring of the gas burner can be located inside or above or below the opening in the glass/glass-ceramic plate.
In a preferred embodiment of the invention the cooking apparatus is formed with a gas burner inside the opening so that the gas burner, which is a cylindrical atmospheric burner, is received in the opening with its burner ring projecting above the cooking surface, and at least one passage in the glass/glass-ceramic plate is formed for conduction of secondary air from the chamber or space under the glass/glass-ceramic plate upward through the plate to the flame region/burner ring of the gas burner.
This concept allows a simple structure for the embodiments of the invention in a cylindrical atmospheric gas burner.
According to a first form of these embodiments the arrangement is designed so that an annular gap for passage of secondary air is formed between the edge of the opening for the gas burner in the glass/glass-ceramic plate and the casing of the gas burner received in it.
According to another form of these embodiments the gas cooking apparatus is designed so that the glass/glass-ceramic plate has a cutout section forming a feed opening for secondary air in the vicinity of the opening for the gas burner and the annular gap between the burner casing and the edge of the opening for the burner is covered by an cover plate.
This latter form eliminates an open or free space between the burner case in the edge of the opening, through which material from the cooking vessels which overflows from them can fall, but necessarily increases expenses for construction of the glass/glass ceramic plate.
In the embodiment with gas burner arranged under the opening the cooking apparatus is constructed according to another form of the invention so that the gas burner is arranged as an atmospheric circular burner under or at the same height as the opening in the glass/glass-ceramic plate and the supply of secondary air to the flame region occurs from the side and/or from under the circular burner.
Alternatively also the cooking unit can be formed so that the gas burner, formed as a hybrid burner, is arranged under or at the same height as the opening in the glass/glass-ceramic plate and the combustion air is supplied from the space under the glass/glass-ceramic plate.
The glass/glass-ceramic plate can be formed so that it is even with or in the same plane as the opening which can be enclosed with an overflow collar. Alternatively to avoid overflow of material from the cooking vessels through the opening in the cooking apparatus the edge of the opening can be curved upward. If necessary a collector device or gutter can be thereby formed, which borders the cooking area.
Because of the method of air supply according to the invention it is possible to provide a new vessel or pot support in which the support height is less than 25 mm, preferably less than 10 mm, so that the danger of instability of the cooking vessels is clearly reduced.
The embodiments described above may be redesigned in a simple manner with non-cylindrical geometries, for example as an oval fish fryer or triangular or square burner.